The research of this proposal is designed to: first, determine the normal filtration characteristics and Starling forces of the pulmonary microcirculation; second, determine how these factors are altered in pathological states (septic, hemorrhagic, and burn shock); and third, to evaluate the effects of conventional and proposed therapeutic regimens on these fluid exchange factors. We will use an intact dog lung preparation, which we have developed to continuously monitor lung weight, to measure the pulmonary capillary filtration coefficient, capillary hydrostatic pressure, and the critical capillary pressure required to cause edema. In addition we will cannulate a small lymphatic vessel at the hilus of the lung in order to measure lymph flow and tissue fluid oncotic pressure. We will measure plasma oncotic pressure. Utilizing this value and the other parameters in the Starling equation mentioned above, we will calculate the tissue fluid hydrostatic pressure. We will also implant small tissue capsules in the lung to measure tissue fluid pressure. By electrophoresis of the lymphatic fluid samples collected at different lymph flow rates we will determine the concentrations of various size proteins in the lymph. Using these values we will determine the permeability characteristics of the pulmonary capillary membrane to different endogenous proteins. Thus we will be able to measure all of the Starling forces as well as determine the permeability characteristics of the capillary membrane in the same preparation. By analyzing both the terms in the Starling equation and the capillary permeability normally and in various pathological states we will be able to determine specifically how edema is produced by the pathology. We will then use these parameters to evaluate the effectiveness of various therapeutic procedures.